src: move trace_event.h include to internal header

[bnoordhuis]

Move the include from src/node.h to src/node_internals.h.

trace_event.h is not shipped in binary-only and headers-only tarballs,
making it currently impossible to build add-ons against them.

cc @richardlau @matthewloring

CI: https://ci.nodejs.org/job/node-test-pull-request/5990/

[matthewloring]

LGTM

[richardlau]

LGTM

[joshgav]

Seems this would make the tracing macros unavailable to native module authors, which I don't think is what we want at least long term. Would it be better to bundle the header?

/cc @nodejs/diagnostics

[matthewloring]

@joshgav I think it would be a good idea to hold off on encouraging native module authors to use these macros directly. Many of the macros are "implementation details" of other macros and not intended to be used outside the file. We should provide a simplified API for recording trace events or provide documentation on the set of macros intended to be part of the public API.

[Qard]

Agreed that we should probably not be exposing the full surface area of the trace_event.h macros. I think it's best we make this fully internal for now and expose a friendlier API to userland in the future.

[joshgav]

@Qard @matthewloring

We should provide a simplified API

expose a friendlier API to userland in the future

Makes sense and I agree in principal, although in the discussion at the last Collab Summit we said we wouldn't wrap the macros or provide an alternate C/C++ API.

[matthewloring]

or provide documentation on the set of macros intended to be part of the public API.

I would also be fine with this approach. Wrapping will incur some performance overhead which we could avoid.

[Qard]

My only issue with leaving it publicly accessible is that people may try to use it in ways not intended or expected. The _headers issue is a good example of that behaviour. Probably not as problematic as _headers was as this is native and in a less popular component, but we should at least have a plan for how to deal with userland exposure, intentional or otherwise.